Ballast resistance



BALLAST RESISTANCE Filed March 28, 1929 (kton/MA1 mma Das 15,1931

BAIUIL Bm, 0l' BOILYN, NEW YORK `BALLAST RESISTANCE appumionmea man as, ma. seran mi. 350,584.

This invention relatesA to a ballast resistance and specifically to one having a wide range of resistance variation with oad. It also relates to a ballast resistance utilizin the temperature resistance characteristics o iron wire in a helium atmosphere.

In the ballast resistance devices of the prior art, especially those used for the control of line voltage applied for the operation of radio sets on commercial lighting circuits, a single iron wire resistance elements in hydrogen has been utilized. While a good control of line voltage to the set can be obtained with such a device,- it has an inherent limitation, namely that the initial current surge throu h the ballast prior to its assuming an equili rium temperature for its power consumption, is so reat that it strains the electrical circuits o the devices controlled, especially the filter circuit elements such as the rectiliers, condensers and cathode heaters.

In the present invention, helium is chosen as the atmosphere, because of its excellent thermal conductivity, and non-ex losive, in-

ert and monatomic character, the atter characteristic aiding in obtaining a better range of resistance change with temperature than is obtained with iron alone and especially because it is not easily absorbed as is hydrogen, which when absorbed, causes the iron to become cr stallized and very brittle. Most of the trouble experienced with hydro en filled ballasts has been mechanical brea age due to the iron becoming very brittle and readily breakin when subjected to vibration, whereas withelium, the iron remains ductile and has a long life.

In o eration of the device of m invention, when t e current is initially app ied, instead of being directl applied to one ballast element, it is app ied to two, which are connected in series. This prevents an excess rush of current and resultant strainin of the load or controlled device which woul otherwise occur due to the resistance being cold. A thermostatic clement is located near one of the resistor elements. When the iron wire resistance elements heat u p, the thermostatic element, due to the heat developed, moves toward a yieldin'g or spring contact which short circuits one of said resistor elements. The heat from the other resistor element maintains the thermostatic element in short circuit position unless there is excess heat,- due to excessive line potential or other causes, in which case the moving thermostatic element moves further and slides past the spring contact, again connecting the two resistor elements in series.I Should the line voltage be reduced to its normal value, the thermostatic element will retract and again short circuit one of the resistor elements.

A ballast tube embodying my invention is shown in the accompanying drawing.

In order to more completely describe the invention, reference is made to the accompanying drawing in which R1 and R2 are the iron wire ballast resist-ance elements, enclosed in a glass tube T, having an inert atmosphere such as helium, preferably at about 100 mm. pressure. Te is a thermostatic element which by effect of heat from the resistance elements R1 and R2 moves toward' and from the yielding contact C. S is the su port for t e resistor elements and L1 and are' the supporting leads in the glass stem. The terminal prongs are designated as T1 and T2.

In operation when current is applied to the terminals, the iron wire resistor elements are heated and due to the high temperature resistance coeiiicient of iron,'there is a regulation vof the currentI flow by an increase in the voltage drop across the resistor elements by said current. I have discovered that with my new ballast tube, an increase of 10% in current will increase the voltage drop across the ballastabout 200%. When the resistor elements are heated to the desired temperature, the thermosta-tic element 'Ie moves toward the contact C and short circuits resistor element R1. This increases the current flow in the circuit to a. value corresponding to a given voltage. Should the line voltage increase beyond the control range of the single resistor element R2, the thermostatic element Te moves beyond the yieldable contact C and separates therefrom. This inserts IR1 in series with R2, thus reducing the line voltage by increasing the resistance in the ballast.

2 rasato@ When the line voltage again returns to its normal value, the thermostatic element moves back to engage the yielding contact vand so again short circults l'eslstcr element R1. I

l`When the operating switch controllin current through the ballast tube is opene the current through the ballast resistance is cut 0E and stopped and the thermostatic element cools down. Contact of the thermostatic element with yieldable member C is broken as element Te in cooling,' moves to the left of member C to its normal position when the tube is not inuse.

While I have illustrated one specific form of my invention, I mean to have the claim cover all features as common equivalents to the elements herein set forth.

I claim:

A ballast tube comprising resistor elements in series and cautomatic means including a thermostat Within the tube to cut out one of said elements as the current therein increases to a certain value and to again insert said element in series as the current is further increased.

In testimony whereof I aix my si ature.

SAMUEL RUTTENB RG 

